https://en.wikipedia.org/wiki/2026_Minab_school_attack
"According to witness accounts verified by satellite-based analyses, the school was triple tapped by three distinct strikes."
War crime isn't just a legal definition, just like the world was genocide-free before WW2. And by your reasoning it's totally fine to genocide people as long as no treaty/law prevents it. Of course it isn't.
Most people would agree to say that bombing a school or a dessalination plant is a war crime, whatever the convention was signed before. Schoolchildren are not responsible for the IRGC's actions.
The other "colloquial" definition of a war crime is "things we prosecuted the Nazis for at Nuremberg".
One side here is playing "world's police", so this "but those people (that we've painted as fundamentalist extremist terrorists) are committing war crimes so why shouldn't we get to, too?" isn't exactly the fine upstanding argument that you seem to think it is, just as it's not when the IDF responds to children throwing rocks at main battle tanks with live ammunition and turning off the power to a country for three days.